1. Field of the Invention
The present invention relates to a color cathode-ray tube.
2. Description of Related Art
In a phosphor screen of a current color cathode-ray tube, for the purpose of enhancing brightness and contrast, a method for providing an optical filter that transmits only light with a desired wavelength between a glass panel and a phosphor has been adopted widely (e.g., see JP 10(1998)-302668 A).
The above-mentioned phosphor screen is produced, for example, as follows. On an inner surface of a glass panel in which a light-absorbing layer such as a black matrix or a black stripe is formed, dot-shaped or stripe-shaped optical filter layers, which selectively transmit only a wavelength of red, green, or blue, are formed. Then, on the respective optical filter layers, dot-shaped or stripe-shaped phosphor layers are formed, which emit red, green, or blue light corresponding to the color of light that is transmitted through the underlying optical filter layer.
At this time, when the phosphor layers are formed directly on the optical filter layers, due to the underlying unevenness, the compatibility between an optical filter material and a phosphor material, and the like, there arises a problem of so-called “dot missing” in which a phosphor peels off the glass panel. This tendency is conspicuous particularly for green and red phosphors.
In order to solve the above-mentioned problem, a method for applying colloidal silica liquid to the optical filter layers, followed by drying, to form a silica layer, and forming phosphor layers on the silica layer has been proposed (e.g., see JP 10(1998)-64427 A and JP 11(1999)-233018 A). The method for forming such a phosphor screen will be described with reference to FIGS. 4A to 4G.
First, a light-absorbing layer (a black matrix or a black stripe) 2 is formed on an inner surface of a glass panel 12 (FIG. 4A).
Then, blue pigment dispersion liquid is applied to the inner surface of the glass panel 12 to form a blue pigment coating layer 3B (FIG. 4B).
Then, a shadow mask (not shown) is attached to the glass panel 12, and the glass panel 12 is exposed to light through the shadow mask (FIG. 4C).
Then, the shadow mask is removed, and a developer such as an alkaline aqueous solution is sprayed onto the glass panel 12 to remove the unexposed blue pigment coating layer 3B, whereby a blue pigment layer (blue filter layer) 4B is obtained (FIG. 4D).
In the same way as in the process of forming the above-mentioned blue filter layer 4B, a green filter layer 4G and a red filter layer 4R are formed (FIG. 4E).
Then, colloidal silica liquid with colloidal silica dispersed therein is applied to the optical filter layers 4B, 4G, and 4R on the inner surface of the glass panel 12, followed by drying, to form a silica layer 5 (FIG. 4F).
Then, a blue phosphor layer 6B is formed on the blue filter layer 4B, a green phosphor layer 6G is formed on the green filter layer 4G, and a red phosphor layer 6R is formed on the red filter layer 4R successively by a slurry method (FIG. 4G).
Thus, a phosphor screen 7 is provided on the inner surface of the glass panel 12.
When the thin silica layer 5 is formed on the optical filter layers 4B, 4G, and 4R as described above, the adhesion force of the phosphor layers 6B, 6G, and 6R is enhanced, which can reduce the peeling of the phosphor layers 6B, 6G, and 6R.
However, according to the above-mentioned method, the process of applying colloidal silica liquid is required, so that a material, a facility, and the like therefor are necessary, which increases cost. Furthermore, after the colloidal silica liquid is applied, excessive colloidal silica liquid splashes on the periphery and is dried to become foreign matter, which causes various kinds of defects to reduce the yield.